Flotation process



Patented June 27, 1939 UNI-TED STATES PATENT OFFICE,

2,163,701 FLOTATION raocnss Robert 0. Ried, West Conshohocken, Pa., assignor to Separation Process Company, a corporation of Delaware No Drawing.

Application September 10, 1937, Serial No. 163,306

4 Claims. (01. 209-166) land cement, and will be specifically described hereinafter in its application tosuch uses, but it will be understood that it is of more general utility W f In many of the natural limestones, marls and chalks, the constituent minerals are so fine that extremely fine grinding is'required .to free the bonds, or at-least'to release a suflicient proportion of the mineral or erals occurring in excessive quantity, to permit the desired elimination, The resulting pulps are not readily amenable to froth flotation because the slimes constitute at least the major quantity. With some of these pulps, a limited .de-sliming can be practiced, ,but frequently this is undesirable in view of weight losses and is impractical where the mineral sizes are such that the actual calcite separations are made in the lower micron ranges of particle size. Especially in cement manufacture, the calcite and quartz slimes should be recovered and utilized because intimate contact ofiine particles is essential to produce uniform and complete reactions in. burning the ultimate mixture to clinker. v v 1 With fewexceptions; natural materials of the class described contain alumina in too great abundance to make them suitable for the manufacture of modern cements of the low-heat of hydration and sulphate resisting types, and in many the proportion of aluminais too large to permit production of cements of moderate heat of hydration suitable forordinary uses, such as highway construction. 'In these -materials, all tangible quantities of alumina are silicates, principally the micas, but other silicates, such as kaolin or kaoliniteand the feldspar minerals,

'etc., are'common and may be present with one or more of the micas. The micaceous matter is readily released in grinding and the proportion in the slimes makes flotation separations dimcult, as the froth is contaminated by particles trapped,'probably mechanically, due to the fineness of the mica particles and their shapes, which give them-a much slower settling rate than the other tailing minerals.

It has been discovered that light stage oiling flo'tationcircuits are essential to effect a satisfactory differential separation of calcite from such pulps. In relatively warm pulps, oleic acid is a satisfactory collector, but as pulp temperatures are reduced, dispersion is incomplete and the consequent partial over-oiling causes decreased grades of concentrates duetopartial' heavy flocculation. Further, the relatively high cost of oleic acid makes its use objectionable for concentrating calcite, particularly in view of the low commercial value of cement. The high titre fatty acids, such as fish oil acids derived from fish scrap, are unsatisfactory as they cannot be uniformly dispersed and cause heavy flocculation, especially in cold water.

It has been proposed heretofore to employ emulsified fatty acids as collectors of other oxide ore minerals, but these lack utility in calcite pulps of the types described. Each of the three "principal types have undesirable characteristics Those stabilized by for the present purposes. amine soaps produce heavy, matted; froths of low-grade, difficult to clean by froth flotation and dimcult to thicken, as heavy scum, carrying up to 5% of the weight of the calcite, floats on tax . the surface of the thickener and cannot be de- I stroyed by spraying or other convenient means.

Further, these emulsions tend to form layers, i. e., are not as stable as those to be described hereinafter. The sodium soaps, used as stabilizers, produce excessive froths that cannot be controlled in stage oiling-circuits and the emulsions' are usually unstable. Emulsions stabilized by sulphonated alcohols produce lowg'grade c'oncentrates and the froths are likewise too voluminous for practical purposes.

It is accordingly'among the purposes of the invention to provide stable oil in water emulsions of the fatty acids, that can be used in high water dilutions to effect complete dispersion in the pulps, and to permit accurate and uniform control of the small quantities introduced at each of the oiled stages, whereby selective differential separations can be made of the calcite from the tailing minerals. It is a further objectiveto produce emcient collectors based on the cheaper fatty acids. It is a further purpose to provide emulsions of low frothing characteristics, whereby the froth balance of the cells can be controlled by additions of the usual frothing agents. It is also a purpose to provide collecting reagents that can be used at all ranges of pulp temperature, including temperatures just above freezing.

In general, the invention comprises the use of oil in water emulsions of fatty acids as collecting reagents for oxide ore minerals, particularly calcite. These emulsions are stabilized by rather critical quantities of a sulphonated oil of a class to be described hereinafter. The aqueous dispersions are relatively high, the ratio of oil to water being in a range of 1:10 to 1:30, and preferably within a range from 1:25 to 1:30, to

permit accuracy in control of quantities and The stabilizingagents used are of the class of sulphonated" vegetable and animal oils, including fish oils. In this class, some are true sulphonated oils, of which sulphonated tea seed oil is probably an example, but others, such as sulphonated castor oil are sulphuric acid esters. The latter are commonly referred to and will be called sulphonated oils herein. The oils of the present invention are accordingly sulphonates or sulphates of glycerides of fatty acids, with more or less free acid.

The proportions ofsulphonated oil required to produce dilute fatty acid emulsions, both stable at normal temperatures, and having desirable flotation characteristics, are rather critical and range from 5-to '7 parts, by weight, to 100 parts, by weight of the fatty acid oils. These proportions are not affected by the titre or the free fatty acid content of the oil, The preferred] proportionis the minimum necessary to stabilize the emulsions, usually 5 parts, such emulsions remaining stable indefinitely at normal temperatures, some of the emulsions kept for three months showing no tendency to break down.

Lesser quantities of the sulphonated .oils do not produce complete stability, particularly in cold weather and in the lower ratios of water dilutions. Proportions above '7 parts are: unsatisfactory, in the fine pulps described, as the excessive quantities result in poor selectivity, due to a pronouncedtendency to produce heavy, matted froths, difficult to clean by froth fiotation,'with or without additional reagentsor reagent quantities. Further, these tough froths are not effectively broken by spraying, and-a considerable weight of the fine calcite is held in the scum floating on the surface of the concentrates thickener.

These emulsions may conveniently be prepared by stirring the sulphonated oil in a drum of fatty acid, the latter being heated if it does not flow freely. 'The mixture may be drawn from the drum by a water eductor of the Venturi pipe, preferably equipped with a pressure gauge on the water inlet side. The quantity of water is proportional to the pressure required to syphon the oil mixture. The quantity of the oil, and consequently the degree of the oil in water dilution or dispersion, is controlled by varying the size of the orifice of the oil suction pipe. By these means, the desired ratioof oil to water can readily be obtained. The mixture of water and oil, as discharged from the eductor is partly emulsified, the dispersion being completed by passing the mixture preferably through a colloid mill, such as a Premier paste mill, having a rotor clearance adjusted to about 0.003", although a homogenize'r may be employed.

For a better understanding of the practice of the invention, reference is made to the following examples:

First example The first example consists of a series of tests which illustrate the selectivity and collecting power of. emulsions stabilized by representative sulphonated oils. It consists of nine tests in which substantially identical specimens of argillaceous limestone were treated under equivalent conditions. The flotation cell feed had the following physical analysis: I

, i Per cent Plus 100 mesh 1.8

Minus 100 mesh plus 200 mesh 11.2

Minus 200 mesh plus 325 mesh 14.0

Minus 325 mesh 73.0

In each test, fish oil fatty acid of 78% free fatty acid content, by titration, was used as the collector in view of its low cost. The pulp temperatures were 60 F., whereby a blank test, No. 9, could be included for purposes of comparison. In this test unmodified (not emulsified) fish acid was used as the collector. This reagent is satisfactory only at elevated temperatures as its selectivity decreases rapidly as pulp temperatures decrease below 60 F. ;Test No. 8 was also included for purposes of comparison to show the low-grade of calcite concentrates obtained with emulsions stabilized by sulphonated alcohols, the agent used being a well-known wetting agent sold under the trade name Aviroll-L144.

In all cases, in Tests Nos. 1 to 8 inclusive, five parts of stabilizing agent to one hundred parts of oil, by weight, were used in an oil in water dilution of 1:30. Flotation time in a Fagergren flotation machine was 5 minutes, the collecting reagent being added in stage oiling in five stages of rougher concentration at 1 minutes intervals.

The frothing agent used was a mixture of branched and straight chain aliphatic mono, hydric alcohols boiling between about 152 ,C.

and about 162 C. obtainable along with methcould be controlled accurately. The alkalinity of all pulps was normal, at pH 7.8. The calcite (00.00;) content of all 'pulps was substantially tons each. The pulp was partially de-slimedby .identical, the average being 68% by titration. hydraulic classification but contained 20% of -.sults of four comparative tests in actual commercial operation. The material treated was arg'lllaceous limestone taken from a'tested stor- I agepile of approximately. 1600 tons to insure almost identical cell feeds for each test, of 400 of .an excessive quantity of one or more of the constituents. Therefore, and depending upon the chemical composition of the limestone, the objectives are either to effect the minimum sepa-' rations necessary in the entire supply of raw ma-.

' Concentrates Rejects x2523 3 5 1:00 o/w emulsion r Test Percent Percent Emul I 1 7% rts ::l 3h2: t$ 0i l V i 32%? 03158. 535%, $5501? 3333: 33 5? F02? 55 1 00.5 05.2 07.4 00.5 22.2 2.0 0.002 0010 000001- 011.

2 77.3 01.0 01.0. 22.7 25.0 0.4 0.007 0. 01s Crude 01-0011. 3 02.0 00.5 00.0 17.0 1 .0 0.0 0.007 0.010 Olive 011.

4 81.4 00.0 0 .0 18. 6 12.0 3.4 0.007 0.515 Teaseed oil. 5 0. 02.0 01.0 00.3 17.5 0.0 1.7 0.007 0.510 God 011. V

0 7 .0 80.4 03.0 20.5 20.3 0.0 0.001 0. 010 010100010. 1 7 02.0 00.5 00.0 17.1 12.0 0.1 0.007 0. 010 Neats-Iodt'oil.

j s 00.7 75.3 00.2 0.3 0.0 0.0 0.001 0.510 sulphonated 01 01101.. v 0 00.4 01. 70.0 00.0 i 44.0 22.0 0.007 0.024 llishacidunmodifled v It will be seen from the foregoingtests-that the total solids in particle size ranges below.37 I the emulsion stabilized-with sulphonated teaseed microns.- The pulp temperatures varied from oil, produced the most satisfactory concentrates, 65 to 68? F., andthe alkalinity was substantially 25 with relation to both grade and weight recovery. constant at pH 7.6. All tests were of 24 hours This is closely followed by the emulsion stabilized duration and were made in normal plant operby cod oil, Test No. 5,-the lower grade being. ation, 'using Fagergren flotation machines. In offset by the increased weight recovery of cal- Tests Nos. 10 and 11, 0.01 lb. of 1L1 alcohol was 39 cite. It should be understood that the concenused as a frother, and in Tests- Nos. 12,and 13, 3o

trates ofthe first seven tests can readily be the quantity was 0.03 lb. per ton of solids. cleaned by froth flotation without additional re-' agents, if it is desired to improve the grade by 0000. Percent discarding additional quantities of the tailing $28 3 2.315935% 3K PXF I IOOOVBIY minerals. It w1ll also be seen that the concena trates of Test No. 8, in which an emulsion sta- 1o 88 0 h bil ized by ,sulphonated alcohol was used are of 'n:::: sa'o 84to86 010100100. the lowest grade. This low grade accounts for the extremely high weight recovery, and it wfll be understood that substantially all of. the fine 13:11:: 513 $332; 33330233535220? minerals were carried over in the excess of froth. The volume of frothiwas too great to 1 1511 011 0100.2 10100110000 fatty acid. permit efiective cleaning. This lack of selec- 01mm tivity is characteristic of. this emulsion, and the The foregoing are average results under usual rgrades are not substantially improued by deconditions in actual cement mill operation, in. 45

' creasing the quantity used. Blank Test No. 9, which the objective was to maintain a constant demonstrates that unmodified fish acid, even in grade-of rougher concentrates closely approacha relatively warm pulp, produces a relatively lowing 88% 'CaCOa. It will be seen that both of grade and a very low weight recovery. Itisto the. emulsions, stabilized by sulphonated caster be borne in mind that the heavy flocculationprooil, were superior in weight recovery to the 50 duced by this collector does not permit effective unmodified fatty acids. It is especially to be froth cleaning. noted that in spite oi'its lower free fatty acid The identity of the sulphonated oils can best content, and particular1y.in view of the relabe understood by reference to the analysis of tively low cost, the best results were obtained the sulphonated cod oil used in the emulsion of with emulsified fish 011, whereas the raw fish 55 Test No. 5, and which is typical, the composition. oil was inferior'to the more expensive oleic acid. of the other sulphonated oils mentioned or'in- 4 To interpret the results of the foregoing tests .cluded in' the table being approximately the properly, it should be borne in mind that for same: purposes of cement manufacture, it is not necesco 0 sarily desirable to produce high grade conceng0 Solutionh ""5555" trates, for both chemical and economical rea- I Fatty acid (free) 1 do sons. The ultimate cement raw material mixture- Ash T"'-"-"'' required for burning consist of four essential i v constituents, three of which may be present in SO: do 3.6 05 Iodine (original) 2 1370 several mineral forms. To obtain favorable kiln Iodine (after 555555," "C" reactions, the fin st particle sizes oi the essential constituents should be recovered and uti- J :Second example lized, without disturbing thenatural mixture, j 9 which has been improved in the course of grind- 7 The second example comprises the essential ing, more than necessary to effect the elimination such practices are obviously desirable.'

Although the calcium carbonate content of the desired .raw material mixtures for all normal types of Portland cement is in the neighborhood of 76%, it will be realized that the grade of concentrates in most cases must be considerably higher, usually. to permit the elimination of excessive micaceous matter, and so that the ultimate mixture can be corrected by high ratio silica derived from the tailings of the flotation operations, or supplied by a. natural material high in silica, such as sandstone, or both.

In the second .example,,the purpose in maintaining'a concentrate grade of 88% CaCOa was to achieve the foregoing objectives in a continuous process inwhich the ultimate mixture is made by combining the untreated fine particles and the flotation concentrates, the relative quantity of the cell feed increasing with respect to the untreated fines as the calcite content of the natural materials decreases, in accordance with the method of Breerwood Patent No. 2,028,313.

I claim:

1. A method of concentrating oxide ore min erals by froth flotation which comprises incorporating in a pulp of the mineral a quantity of an aqueous emulsion of a fatty acid stabilized by to '7 parts of a sulphonated glyceride oil selected from the class consisting of the vegetable, animal and fish oils to 100 parts of fatty acid oil, by weight, and subjecting the pulp to froth flotation.

2. A method of concentrating oxide ore minerals by froth flotation which comprises incorporating in a pulp of the mineral a quantity of an aqueous emulsion of a fatty acid stabilized by approximately 5 parts of a sulphonated glyceride oil selected from the class consisting of the-vegetable, animal and flsh oils to 100 parts of fatty acid oil, by weight, and subjecting the pulp to froth flotation.

3. A method of. concentrating oxide ore minerals. by froth flotation which comprises incorporating in a pulp of the mineral a quantity of an aqueous emulsion of a fatty acid stabilized by 5 to 7 parts of a sulphonated glyceride oil selected from the class consisting of the vegetable, animal and flsh oils, to 100 parts of fatty acid oil, by weight, in which the oil in water ratio is within the range of 1:20 to 1:30, and subjecting the pulp to froth flotation.

4. A method of concentrating finely divided calcite by froth flotation from argillaceous pulps containing a substantial proportion of slimes, which comprises incorporating in apulp, in a stage oiling froth flotation circuit, quantities of an aqueous emulsion of flsh oil fatty acid stabi- ROBERT C. RIED. 

